A generic motor is described, for example, in the document EP 2 135 567 A1. In this known case, however, the structure is such that the stator winding is embedded in a cast compound.
Compared to this, modern motors include a coil former usually made from plastic material by injection molding to which at least one stator winding is applied. Said design enables the at least one stator winding to be accommodated in the motor in an even more space-saving manner. At the same time, the manufacturing costs can be reduced the coil former being injection-molded in a more and more complex shape which enables the coil former to be permanently fixed in the motor housing and the coil winding having a predetermined configuration to be permanently fixed without any additional components.
In order to further increase the output of said motors efforts are made to further reduce the air gaps between the rotor and the coil former, for example to ranges of from 0.1 to 0.3 mm, taking the further special feature into account that the coil formers frequently have a considerable axial length as compared to the inner diameter. It has turned out that in conventional motors of this constructional design sudden blocking of the rotor entailed early failure.